The invention relates to a locking device for a seat back of a motor vehicle seat.
Folding seat backs for motor vehicle seats allow access to the rear in two-door vehicles. Actuation of the locking device to fold the seat back in the direction of the seat cushion of the seat part is generally accomplished by means of an unlocking lever projecting the door side from the side of the seat back. In vehicles with higher comfort, in addition to the unlocking lever on the door side, an additional unlocking lever is provided on the other side of the seat back so that the driver for example is able to unlock the seat back of the passenger seat from the driver's seat without having to reach behind or over the seat back.
In a known unlocking device of this kind described in German Patent Document DE 30 42 713 A1, the ends of a wire cable are fastened to locking latches pivotably mounted on the left and right sides of the seat back frame, said cable being guided over two segment-shaped guide parts. Each guide part is formed on one of the two unlocking levers at a distance from its pivot point on the seat back frame. Thus, the wire cable runs in two lengthwise segments extending along the length of the sides of the seat back frame and in a transverse section that extends parallel to a cross member connecting the sides of the seat back frame. When the left or right unlocking lever is raised by hand, the guide part moves upward on a circular path around the pivot point of the unlocking lever. As a result, both the lengthwise section running beneath the moved unlocking lever and the opposite lengthwise section of the wire cable are pulled upward, so that the two locking latches are raised and the seat back is unlocked from the seat part.
A tensioning device is provided in the transverse section for exact adjustment of the total length of the wire cable. In this manner, play in the wire cable that can lead to rattling sounds in the pivot levers is eliminated. To compensate for play, the seat back must first be mounted on the seat part while the wire cable with its tensioning device is still freely accessible. Only then can the seat back be completely upholstered.
For reasons of cost and manufacturer, a modular design is desirable nowadays in seat manufacture, with the seat back and seat part being manufactured separately, as regards both their frames and their upholstery, and then assembled. Mechanical systems like the locking device for the seat back must therefore be preinstalled in the seat back before the upholstery is added and must already have been adjusted, since access to the adjusting device along the wire cable is no longer possible afterward.
An object of the invention is to provide a locking device of the type referred to above in which any manufacturing tolerances that remain in the locking device can be compensated even after complete upholstering of the seat back.
This object is achieved in a locking device constructed according to the invention by an arrangement including a locking device for a seat back of a motor vehicle seat, pivotably articulated to a seat part with a seat back flame covered by a seat back cushion, with at least one locking latch, pivotably mounted on the seat back frame, for engaging a locking pin mounted on the seat part, with two unlocking levers pivotably mounted on the seat back frame, one of which levers projects on the left side and the other on the right side of the seat back, each from an opening made in the seat back cushion for manual operation, and with a flexible tensioning element to connect the unlocking lever with the locking latch, wherein the tension element is a tension cable guided in two separate flexible sheaths, one of said sheaths being fastened near the first and second unlocking levers and the second sheath being fastened near the second unlocking lever and the locking latch, each endwise on the seat back frame, and wherein one end of the tension cable is fastened to the first unlocking lever au a distance from its pivot point and the other end of the tension cable is fastened to the locking latch at a distance from its pivot point, said tension cable being guided over a preferably rotatably mounted deflecting roller mounted on the second unlocking lever at a distance from its pivot point.
The locking device according to the invention has the advantage that, due to the continuous tension cable, any tolerances in the locking device that result from one end of the tension cable remaining always accessible at the locking latch can be eliminated by tightening the tension cable, simultaneously preventing any rattling sounds in the unlocking levers, even when pivoting the seat back. When the first unlocking lever is lifted, the tensile forces are conducted by the tension cable that is guided over the deflecting roller on the other pivot lever toward the locking latch. The opposite force thus acting on the roller bearing causes the second unlocking lever to be pulled downward and to be held, rattle-free, in its resting position in the seat back. Lifting the second unlocking lever conducts tensile forces directly into the locking latch. The opposite force in the tension cable means that the first unlocking lever is then puller downward and held, rattle-free, in its resting position n the backrest. The resting positions of the two unlocking levers are therefore always defined exactly.
In a preferred embodiment of the invention, the distance of the mounting point of the tension cable of the first pivot lever from its pivot point on the seat back frame is twice as great as the distance of the bearing point of the deflecting roller on the second pivot lever from its pivot point on the seat back. This means that the actuating forces to be applied to unlock the locking latches are approximately the same at both unlocking levers.
If, according to another embodiment of the invention, the distance of the mounting point of the tension cable on the first pivot lever from its pivot point on the seat back is increased by an additional amount, chosen so that the higher frictional forces acting on the first unlocking lever because of the greater length of the tension cable are compensated, the actuating forces to be applied to both unlocking levers are exactly the same.
In a preferred embodiment of the invention, the pivot levers are designed as single-armed levers and the pivot points of the frame side for the unlocking levers are located at or near one end of the levers. The application point of the tension cable on the first lever and the hearing point of the deflecting roller on the second lever are therefore located between the respective pivot point of the unlocking lever of the vehicle frame and the grip at the end for actuating the unlocking lever.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.